Typical 50 ohm low-band (850 & 900) planar inverted-F antennas (PIFAs) used in mobile phones have a single resonance and, consequently, a low bandwidth in the order of 50–60 MHz. Standard PIFA implementations are not capable of simultaneously covering both 850 band and 900 band (with a total required bandwidth of 136 MHz, from 824 MHz to 960 MHz). Available bandwidth could be increased by using a longer ground-plane or a higher antenna, but in most cases the ground plane length is limited to 100 mm and the antenna should be no higher than 5–6 mm. In these cases, getting enough bandwidth for both 850 and 900 is not possible without the use of load switching, for example. In 2 GHz area, it is possible to use a parasitic element in standard PIFA implementations to achieve dual-resonance. However, it is not feasible to use a parasitic element for the 1 GHz range because a much larger parasitic element is needed.
Thus, it is advantageous and desirable to provide a wide-band antenna for use in a mobile phone to cover both 850 band and 900 band, preferably from 824 MHz to 960 MHz.